Method and system for supporting the communication of presence information regarding one or more telephony devices

ABSTRACT

A system for detecting and communicating the presence of one or more computing devices is presented. The invention also presents a method and system for aggregating presence information generated by multiple devices associated with a single user. A server acting as a presence agent on behalf of a first user receives and responds to a subscription request generated by a computing device operated by a second user that wishes to be permitted as a watcher of the first user. When the second user corresponds to access preferences specified by the first user, a notify message is sent to the second user&#39;s device that includes presence information indicative of an activity level and availability level associated with the first user. When the first user employs multiple computing devices, the server generates an aggregate presence document that is representative of the overall presence of the first user.

TECHNICAL FIELD

[0001] The invention relates generally to communication between computers over a network, and more particularly, to methods and systems for communicating the presence of one or more devices from over the network.

BACKGROUND OF THE INVENTION

[0002] With today's widespread use of the Internet as a primary communication medium, pre-existing communication devices are now being designed so that they are capable of communicating over packet-switched networks. For instance, telephones, pagers, cell phones, handheld computers, and even fax machines can now be accessed and controlled from over the Internet. Communication over a packet-switched network using communication devices that traditionally communicate over a circuit-switched telephone network is generally known as network telephony, or IP telephony when an IP network is involved.

[0003] A user having several communication devices (e.g., a cell phone, laptop and handheld PC) can configure each of these devices to identify itself to the network using a single alias or identifier (e.g., username@b.com). In this way, the user is not limited to communicating with others via a single device, but instead has the ability to communicate via several different devices. Nonetheless, the ability for a user to have several devices “present” on a computer network creates a need for other users to be able to determine the status or state of the user's many devices.

[0004] “Presence” refers to the availability, proximity, activity level or operating state of a user on a network. The ability for users to monitor each other's presence is a feature offered in connection with many applications that support network telephony. For example, instant messaging applications such as MSN or Yahoo have an “available buddy” feature, in which a user of the application can determine whether select users are available for engaging in communication. The data retrieved and returned to the buddy list, e.g. “John OFFLINE” or “Susan ACTIVE,” is known as “presence information,” and is generally maintained by a program called a “presence agent.” According to most conventional network configurations, the presence agent is implemented as a dedicated server. Typically, the presence agent supports network telephony protocols such as the session initiation protocol (SIP). Device users can register their devices with the presence agent (e.g., via a registrar module) in order to have their presence maintained and to allow various programs on the network to facilitate network telephony services. As such, a first device user wishing to detect the presence of a second device user does so by “subscribing” with the presence agent, such as via a SIP SUBSCRIBE message. The presence agent intermediates between the first user, also known as the watcher, and the second user to facilitate the communication of the second device user's presence information to the first device user.

[0005] The ability of a presence agent to accurately determine and maintain presence information for one or more users significantly enhances communication and task completion over the network. For example, a very mobile user may only be on the network at certain times throughout the day, and may be accessing the network from varying locations. By subscribing as a watcher of this mobile user, it becomes possible for another user to detect the presence of the mobile user during the times at which the mobile user's computing device is actually connected to the network. So, when the mobile user is present, the watcher can correspond instantly with the mobile user via a chat session or videoconferencing call, as opposed to resorting to a non-real-time communication such as e-mail messaging. Hence, presence is an especially important factor for facilitating communication between users. Unfortunately, however, conventional presence agents are unable to determine presence with sufficient granularity. As an example, consider a scenario where a second user has subscribed with a presence agent as a watcher of a first user. If the first user is in the second users' available buddy list, and the first user's computing device suddenly goes into sleep mode, the second user's buddy list should still indicate that the first user's device is available for communication rather than indicate that the first user's device is “offline.” An indication of “offline” does not accurately reflect that the first user's device may still be connected to the network and may still be able to receive messages. Yet, many presence agents only provide generalized presence information, such as “offline” or “unavailable,” and do not account for more ambiguous presence conditions.

[0006] Some other presence agents attempt to more accurately present presence information by shortening the subscription periods of watchers. According to this mode of operation, when a watcher subscribes with the presence agent, the watcher's subscription time is minimized (e.g., by using a shortened timeout period), and so the watcher must frequently renew the subscription. Each time the watcher renews, the watcher receives the most current presence information. While this method of presence determination can be effective for detecting subtle changes in presence, the constant updating of subscriptions causes the presence agent to use more bandwidth and increases its overall processing time. Furthermore, this method increases the message load on a server that operates the presence agent resulting in a significant reduction in scalability.

[0007] Still further, many presence agents are unable to provide accurate presence information for those users who have several devices registered and present upon the network. Current standards for retrieving presence information pertaining to multiple device users simply call for the presence of each individual device to be determined, and then presented to the watcher as a compound document, such as an HTML file. As a result, the watcher that receives the compound document indicating the presence information for each device must “guess” which device's presence information most accurately reflects the presence of the user. However, just because a user's mobile phone, pager, laptop, PDA, and desktop computer are all present on the network does not mean the user is using all of them. Indeed, the presence information of the individual devices says very little about the actual presence (e.g., activity or availability) of the user.

SUMMARY OF THE INVENTION

[0008] The invention presents a method and system for detecting and communicating the presence of one or more users on a computer network. This includes users who employ devices that communicate over a network via the SIP protocol, and other common network protocols. The present invention also relates to a method and system for aggregating the presence information of multiple devices associated with a single user such that more accurate and useful presence information pertaining to the user can be determined.

[0009] In accordance with an embodiment of the invention, a network device, such as a server, is equipped with a presence agent that facilitates the exchange of presence information between a first user and a second user. The first user is referenced by a unique alias, such as user@some_network.com, and has one or more computing devices registered with the network server (e.g., via a registration module or dedicated registrar server). When the second device wishes to access presence information pertaining to the first user, the second user employs a computing device to send a subscription request to the network server in order to become a “watcher” of the second device user. Once received, the subscription request is then forwarded to the presence agent operating upon the network device for processing. The network device then generates and submits an acceptance message to the first user's device, followed by a standard NOTIFY message. As such, acceptance of the subscription is sent to the second user regardless of whether or not the second user is actually granted access to the presence information, as determined according to access preferences specified by the first user.

[0010] In order to grant access to the second user, the presence agent checks an access control list (ACL) that comprises one or more access rules or preferences. The first user defines these rules in order to affect how its presence information is shared with one or more watchers. When the ACL specifies that the second user may access the presence information, the NOTIFY message includes a presence document that contains the presence information. In contrast, when the ACL specifies that the watcher is not to access the presence information, the NOTIFY message is sent to the watcher without the presence document. Because the network server always sends an acceptance and notification message to the watcher, the subscription process is facilitated without any intervention by the first user, thus minimizing the processing requirements of the presence agent.

[0011] In accordance with another embodiment of the invention, the presence agent operating upon the network device maintains an offline subscribes data structure for storing information associated with any subscription requests submitted by one or more users wishing to access the first user's presence information. The subscription information is stored into the data structure whether the first user to be watched is or is not present (e.g., inactive, logged off), and includes data such as a URI (uniform resource locator) that uniquely identifies a particular subscriber. As such, when resuming upon the network again, the first user's one or more computing devices send a subscribe request to the network device in order obtain any data stored in the offline subscribes data structure. In response to this request, the presence agent operating upon the network device accesses the offline subscribes data structure, extracts the data, and forwards a NOTIFY message to the first user's device along with the data. When the first user authorizes the subscription, the registered device user updates its presence document, and forwards it to the network device. The network device then updates the ACL accordingly, and a NOTIFY message is sent to the subscribing user along with a presence document containing the presence information. On the other hand, when the subscription is not acceptable, the ACL is updated to specify prevention of access by the subscriber, resulting in a NOTIFY message being sent to the subscriber without any presence information.

[0012] In yet another embodiment of the invention, an aggregator component executed by the network device aggregates the presence information of several devices associated with a user into a single presence document. For user's that employ several computing devices (e.g., PDA, cell phone, laptop, and pager), a presence document for each individual device is generated and sent to the presence agent operating upon the network device for processing. Upon receiving these documents, the network device executes an aggregator component that performs a computation to determine the presence priority setting of each document. The presence priority setting of a document is a value that is determined according to attributes that include an activity level and an availability level. The activity level indicates what action the first user or corresponding device may be engaged in (e.g., idle, away), giving an indication of the likelihood of calls or messages actually being accepted from over the network. In relation to the activity level is the availability level, which indicates whether the user or user's corresponding computing devices may actually receive calls based on various network conditions (e.g., offline, online). A description attribute may optionally be associated with the activity or availability level to provide a functional or plain-language description of the assigned level. By summing up these values, the aggregator component identifies which device has the highest presence priority setting, and merges the presence information of each device into a single, or aggregate, document. The resulting presence information contained within the single document indicates to the watcher which of the user's devices most accurately reflects the presence of the user.

[0013] Additional features and advantages of the invention will be made apparent from the following detailed description of illustrative embodiments that proceeds with reference to the accompanying figures.

BRIEF DESCRIPTION OF THE DRAWINGS

[0014] While the appended claims set forth the features of the present invention with particularity, the invention, together with its objects and advantages, may be best understood from the following detailed description taken in conjunction with the accompanying drawings of which:

[0015]FIG. 1 is an example of a computer network;

[0016]FIG. 2 is an example of a computer;

[0017]FIG. 3 is a diagram illustrating a server facilitating a call between a first computing device and a second computing device over the network in accordance with an embodiment of the invention;

[0018]FIG. 4 is a diagram illustrating the mechanism employed by a first computing device of FIG. 3 for setting presence with a server according to an embodiment of the invention;

[0019]FIG. 5 is a diagram illustrating the mechanism employed by a first computing device of FIG. 3 for setting access preferences with a server according to an embodiment of the invention; and

[0020] FIGS. 6-8 illustrate the operation of an aggregator component for processing one or more presence documents.

DETAILED DESCRIPTION OF THE INVENTION

[0021] The invention relates to a method and system for detecting and communicating the presence of one or more users on a computer network. Also, the invention relates to a method and system for aggregating the presence information of multiple devices associated with a single user such that overall presence information pertaining to that user can be determined. In the context of the invention, presence information describes any data that specifies the availability, proximity, activity level or operating state of a computing device or corresponding user of the device from over the network. For example, presence information can be provided to a user of a computing first device (a watcher) in the form of a presence document, and analyzed by watcher to determine if a user of another computing device (a registered device user) is online or offline, busy or idle. This determination is dependent on various factors, including the current activity of the user being maintained, the present operating state of the computing device of the user being monitored, etc. In an effort to stay consistent with common terminology used in the computing industry, this detailed description will use the term “presence” synonymously with the term “presence information” at various times. Moreover, the terms “presence” or “presence information” should be interpreted as relating to the user, or one or more devices employed by the user.

[0022] Also, the invention will be described throughout the course of the description with respect to SIP as a messaging protocol for supporting communication between devices in accordance with the teachings of the invention. Once again, those of skill in the art will recognize that SIP is only one protocol suitable for supporting network telephony and presence, and that other protocols may just as easily be utilized. Other such protocols include the H.323 standard and the Single Computer Telephony Protocol (SCTP). The invention is not limited to any one protocol or messaging implementation, as any means or medium by which two or more devices may communicate to support network telephony applications is suitable. Furthermore, the invention is not limited to any particular network telephony configuration, as any means for exchanging messages between one or more computers via SIP or the like is suitable for use in connection with the invention. This includes network configurations where computing devices such as proxies, redirect servers, registration terminals, presence servers and agents, and one or more clients or “presentities,” are involved in the communication.

[0023] As used herein, the term “network telephony” relates to any process wherein a network, such as the Internet, is used as a transmission medium for placing telephone calls or facilitating multimedia sessions between two or more computing devices. This can include multimedia sessions where streaming media (e.g., audio and video data) is exchanged over the network, conference calls, virtual meetings, and other telephony sessions. The term “network telephony” is generic, and can therefore describe or pertain to several other communication processes involving the exchange of packetized data. These include, but are not limited to, IP telephony, Voice over the Internet (VOI) and Voice over IP (VoIP). Also, as used herein, the term “call” (e.g., telephone call) relates to a session in which an exchange of information is commenced or initiated between two or more computing devices over a network, such as with the aide of a telephony application (e.g., MICROSOFT NETMEETING TM). In the context of the present invention, a “call” is synonymous to a “message” being sent between devices, and those terms will be used interchangeably at times to describe the interaction between two or more devices over the network.

[0024] An example of a networked environment in which the invention may be used will now be described with reference to FIG. 1. The example network includes several computers 20 communicating with one another over a network 30, such as the Internet, as represented by a cloud. Network 30 may include many well-known components, such as routers, gateways, hubs, etc. and may allow the computers 20 to communicate via wired and/or wireless media.

[0025] Referring to FIG. 2, an example of a basic configuration for a computer on which the system described herein may be implemented is shown. In its most basic configuration, the computer 20 typically includes at least one processing unit 42 and memory 44. Depending on the exact configuration and type of the computer 20, the memory 44 may be volatile (such as RAM), non-volatile (such as ROM or flash memory) or some combination of the two. This most basic configuration is illustrated in FIG. 2 by dashed line 46. Additionally, the computer may also have other features/functionality. For example, computer 20 may also include additional storage (removable and/or non-removable) including, but not limited to, magnetic or optical disks or tape. Computer storage media includes volatile and non-volatile, removable and non-removable media implemented in any method or technology for storage of information such as computer readable instructions, data structures, program modules, or other data. Computer storage media includes, but is not limited to, RAM, ROM, EEPROM, flash memory or other memory technology, CD-ROM, digital versatile disk (DVD) or other optical storage, magnetic cassettes, magnetic tape, magnetic disk storage or other magnetic storage devices, or any other medium which can be used to stored the desired information and which can be accessed by the computer 20. Any such computer storage media may be part of computer 20.

[0026] Computer 20 may also contain communications connections that allow the device to communicate with other devices. A communication connection is an example of a communication medium. Communication media typically embodies computer readable instructions, data structures, program modules or other data in a modulated data signal such as a carrier wave or other transport mechanism and includes any information delivery media. By way of example, and not limitation, communication media includes wired media such as a wired network or direct-wired connection, and wireless media such as acoustic, RF, infrared and other wireless media. The term computer readable media as used herein includes both storage media and communication media.

[0027] Computer 20 may also have input devices such as a keyboard, mouse, pen, voice input device, touch input device, etc. Output devices such as a display 48, speakers, a printer, etc. may also be included. All these devices are well known in the art and need not be discussed at length here.

[0028] In accordance with an embodiment of the invention, a server provides presence information regarding a first computing device, which is registered with the server, to a second computing device which operates as a watcher, as illustrated in FIG. 3. The server, labeled 102, is a computing device that is capable of processing messages conforming to a protocol for supporting telephony (e.g., SIP, H.323). The first computing device, labeled 104, and the second computing device labeled 106 are devices capable of communicating with one another over a computer network using network telephony. A first user 103 uses the first computing device 104, while a second user 107 uses the second computing device 106. In order to support the communication of presence information, the server 102 includes various components, such as a program referred to as a presence agent (PA) 152, a registration program (R) 154, and an access control list (ACL) 156. The presence agent 152 receives requests for presence information from one or more computing devices that act as “watchers,” responds to the requests, and generates notifications of changes in the presence of computing devices being “watched”. To maintain that presence information, the server 102 includes a memory 158 for storing the data. The registration program 154 processes registration request messages (e.g., an SIP REGISTER messages) received from over the network. Registration messages are sent to the registration program 154 by computing devices that are new to the network, and serve to “introduce” such new devices to the presence agent program 152. Operating in connection with the presence agent 152 and registration program 154 is the access control list 156. The ACL 156 may be implemented as a data structure, database, or even as a program, and is referenced by the server 102 to allow the server 102 to determine how it is supposed to interact with other devices on the network.

[0029] As shown in FIG. 3, the first user 103 operates the first computing device 104 to establish register with the server 102. The registration program 154 handles this registration process. In some embodiments, the registration program 154 is implemented as a dedicated computing device known as a registrar (not shown), which operates in conjunction with a proxy server that handles SIP messages. Any mechanism by which the first user 103 may register one or more devices in order to facilitate network telephony services, and particularly the communication of presence information, is within the scope of the invention.

[0030] The first computing device 104 executes a program, referred to as a presence user agent (PUA) that generates presence information relating to the first user 103. The PUA may be implemented on hardware/firmware as part of a stand-alone program or operating system. It may also be implemented as part of other software applications such as e-mail utilities, instant messaging software, network monitoring programs, video/audio conferencing programs, etc. When the second user 107 wishes to gain access to the presence information of the first user 103, the second user 107 interacts with the second computing device 106 to generate a SUBCRIBE message. The second computing device 106 sends the message to the server 102 (event 120). The SUBSCRIBE message alerts the server 102 that the second user 107 wants to “subscribe” as a watcher of the first computing device 104 and the corresponding first user 103. In various embodiments of the invention, the subscribe message contains an event header that specifies presence as the basis for the subscription request (e.g., event.presence). The event header causes the presence agent 152 to initiate a call to the server 102 to process the message as a presence subscription (as opposed to some other type of network event). In response to the subscription request, the server 102 (acting as a presence agent on behalf of the first computing device 104) stores the contents of the request into a data structure 150, referred to as an offline subscribes data structure. The offline subscribes data structure 150 is implemented as a file, record, table, index or any other scheme or mechanism for organizing data. Subscription information pertaining to each subscriber (e.g., URI, network address information of the subscriber) is stored in the offline subscribes data structure 150, allowing it to act as a persistent record of the subscription requests. In this way, the subscription information is maintained so as to be readily accessible to the presence agent 152.

[0031] After the subscription request is stored into the offline subscribes data structure 150, the server 102 makes a determination as to whether to accept the subscription request. This determination is made according to rules or conditions defined by the first user 103, which are maintained in the access control list (ACL) 152. In general, the ACL 152 includes access preferences that informs the server 102 as to which permissions, or access rights, a particular user or group of users has with respect to a particular resource-in this case, the presence information related to the first computing device 104 and first user 103. The actual settings of the ACL 152 as defined by the first computing device 104 will be described in a later section of this description. When the subscription message is accepted, the presence agent 152 generates an acceptance message, such as a SIP 202 message (event 124) and a NOTIFY message (event 126), which the server 102 sends to the second computing device 106. For standard telephony protocols such as SIP, the body of the NOTIFY message contains the presence information of the first computing device 104 and/or of the corresponding first user 103. If the presence agent 152 rejects the request, the presence agent 152 generates an acceptance message (e.g., a SIP 202 message) in the same manner as when the request is accepted. However, the server 102 does not send presence information to the second computing device 106, but rather sends a NOTIFY message containing no presence information. As a result, the second user 107 is allowed to subscribe as a watcher of the first user 103, but does not gain access to the presence information.

[0032] According to an embodiment of the invention, access to presence information pertaining to the first user 103 and/or the corresponding first computing device 104 is limited only to those users specified by the ACL 156. Since the server 102 accepts all subscription requests, access to the presence information of the first computing device 104 and/or the first user 103 is not dependent upon the first computing device 104 or first user 103 actually being present. In other words, it is possible for the first computing device 104 or first user 103 to not be present upon the network (e.g., logged off, disconnected, or in a busy state) without jeopardizing the ability of another device to subscribe as a watcher. In conventional systems, the absence of the first computing device 104 results in all SUBSCRIBE requests received by the server 102 being rejected. Consequently, in such systems the watcher must resubmit the request periodically until the subscription is finally accepted. Obviously, this is not desirable as this phenomenon increases the amount of traffic to be handled by the server 102, and, ultimately reduces its scalability.

[0033] The server 102 overcomes this challenge through the use of the offline subscribes data structure 150. When the first computing device 104 and the first user 103 resume their activity upon the network after having previously not been present upon the network, the first computing device 104 sends a SUBSCRIBE request to the server 102 to obtain any data stored in the offline subscribes data structure 150 (event 128). This subscribe request differs from the subscription request transmitted by the second computing device 106 for obtaining presence information (event 120). In that, the subscribe message sent by the first computing device 104 indicates to the server 102 that the first computing device 104 wishes to determine which other devices, if any, have attempted to monitor its presence or that of the first user 103 during the offline period. In response to this request, the server 102 accesses the offline subscribes data structure 150, extracts the data, and forwards an acceptance message to the first computing device 104 followed by a NOTIFY message (events 130 and 132). The body of the NOTIFY message contains the data from the offline subscribes data structure, such as a list of the subscribers and their corresponding network address information. Armed with this information, the first computing device 104 is able to recognize all of the computing devices and users that subscribed as watchers during the time it was not present on the network.

[0034] Once the first computing device receives the list of subscribers obtained from the offline subscribes data structure, the first computing device 104 and/or the first user 103 determines whether to accept or reject the subscription requests. The first user 103 makes this determination by responding to message prompts generated to a display screen 110 of the first computing device 104 by a presence enabled program (e.g., the PUA). In this scenario, the first user 103 responds using an input device such as a mouse or keyboard. Subscription requests can also be accepted or rejected by the first computing device 104 automatically, without user intervention, according to the preferences or auto-settings of the first computing device 104. When a subscription request is accepted, the first computing device 104 generates an updated presence document, which is a file that contains the presence information, and forwards it to the server 102 (event 134). The presence agent 152, operating on the server 102, processes the contents of the presence document, and stores the presence information obtained from the document into an accessible memory location 158 for subsequent retrieval. Also, upon receiving the presence information, the ACL 156 is updated to indicate that the second user 107 has been permitted to act as a watcher of the first computing device 104 and the first user 103 (event 136). As such, the second computing device 106 may freely access the presence information of the first computing device 104 and first user 103. On the other hand, if the subscription is not accepted, the ACL 156 is updated to indicate that the second user 107 is not to have access to the presence information (event 136). No subsequent NOTIFY message is sent to the second computing device 106 in this case, ensuring that the second user 107 is not aware of the presence of the first computing device 104 or first user 103.

[0035] In the foregoing paragraphs, the operation of the server 102 for facilitating the communication of presence information is described. To ensure the most accurate portrayal of presence information to a watcher, in various embodiments of the invention the first computing device 104 is able to insert descriptive presence information into any updated presence document and transmit the presence document to the server 104 to the presence agent 152 Further, the server 102 recognizes the differences between the updated presence document and previous versions of the presence document to the presence document and based on these differences, more accurately portrayal the presence of the first computing device 104 and/or the first user 103. Also, the first computing device 104 is able to update the ACL 156 to control the extent to which other devices may access the presence information maintained by the server 102. In the following paragraphs, the mechanisms employed by the first computing device 104 and server 102 for setting presence and controlling access to the presence information is described. This functionality is presented in FIGS. 4-5.

Setting and Updating Presence Information

[0036] Referring now to FIG. 4, a computer network includes a first computing device 200 that is operated by a first user 200, a server 201, and a second computing device 211 having that is operated by a second user 210. Each of these components has much of the same functionality as those of FIG. 3, with additional features described in the following paragraphs. The first computing device 200 is capable of generating presence information and exchanging it in the form of a presence document with the server 201 in accordance with an embodiment of the invention. The presence document 207 contains information pertaining to the presence of the first computing device 200 and first user 202. Specifically, the first computing device 200 submits the presence document by sending a SERVICE message 204 to the server 201 (event 300). The service message 204 conforms to a standard telephony protocol format such as SIP, and comprises instructions within the message body for initiating the Set Presence remote procedure call. The Set Presence procedure call is a function or method executable on the server 201, that causes the agent 152 operating on the server 201 to set (update) the presence information for the first user 202 and the first computing device 200 in memory 158. Preferably, the service message supports the exchange of complex object types and not just text. Suitable protocols or mechanisms for supporting the transmission of complex objects include, but are not limited to, Internet Inter-ORB Protocol (IIOP), COM/DCOM based protocols, and the Simple Object Access Protocol (SOAP). In the illustrated embodiment, the Set Presence procedure call is contained within a SOAP envelope within the message body. SOAP allows remote procedure calls to be embedded within messages (as a SOAP envelope), and invoked by a receiving device. Several Set Presence calls may be indicated within a single SOAP envelope in order to permit several devices to update their presence information simultaneously.

[0037] In further accordance with an embodiment of the invention, the presence document 207 generated by the first computing device 200 is comprised of one or more attributes that relate to the presence of the first computing device 200 or corresponding first user 202. Such attributes include an availability level 208 and activity level 209. Also, in association with the availability level 208 and activity level 209 is the description attribute 210. The description attribute provides a functional or plain-language description of the assigned activity or availability level, and is specified at the discretion of the first computing device 200. For each presence document generated by a computing device related to the first user 202, one activity level and availability level is specified. By specifying these attributes within the presence document 207, the server 102 is able to provide a more accurate indication of the presence for the first computing device 200 or first user 202 to a user 211 that is acting as a watcher.

[0038] The availability level 208 is an attribute that indicates whether the first computing device 200 or first user 202 may actually receive calls. The first computing device 200, specifies various availability levels, including those shown in TABLE 1 below. Yet, only one availability level need be specified for a single device at a time. TABLE 1 Availability level settings Associated Availability Description of Level Availability Level Explanation 000 Offline The user cannot receive calls. 100 Undetermined The user may be online, but there is no way to know until a call is attempted. 200 Connected The user has a device currently connected that can receive calls. 300 Online The user is in proximity to a device that can receive calls.

[0039] The availability levels are spread into classes, where each class is a multiple of 100. This is analogous to the response code numbering system used in communication protocols such as the hypertext transfer protocol (HTTP) and SIP. Those skilled in the art will recognize, however, that different values or classes may be used to specify the availability level of the first computing device 200, and that the invention is not limited to any specific implementation. For example, the first computing device 200 may want to indicate a greater level of availability than “online,” but may not want to show an availability of “always,” and create a new availability value 250: “likely to take call”. If the second computing device 211 is not familiar with this particular attribute receives such presence information, it can abstract it to a class in which is it familiar (e.g., it can generalized to 200: “connected”).

[0040] The activity level 209, provides an indication of the action in which the first computing device 200 or corresponding first user 202 is engaged. Also, the activity level 209 indicates to the second computing device 211 or other devices that are in the role of watchers the likelihood of calls or messages being accepted by the first computing device 200 or first user 202. Various activity levels may be specified within the presence document 207, as shown in Table 2 below. TABLE 2 Activity level settings Associated Activity Description of Level Activity Level Explanation 000 No explicit There is no information about the activity activity of the user. 100 Away The user is away from the device 150 At lunch The user is taking a lunch break 200 Idle No specific activity is currently being engaged 300 Temporarily un- The user is not available at the present time available 400 Active The user is active 500 In call The user is already participating in a communications session. 600 Busy The user is busy 700 Do not disturb The user does not want to participate in a communication session 800 Always User will stop whatever they're doing to interruptible receive a call.

[0041] Again, those skilled in the art will recognize that the invention is not limited to the set of values or activity classes shown in TABLE 2. Also, it will be recognized by those skilled in the art that specifying the activity level 209 of the 208 first computing device 200 or user 202 in connection with the availability level ensures for more accurate presence. This is in contrast with many existing systems for conveying presence information, in which less useful presence attributes are provided. For example, if a presence document only indicates that the user is “busy,” this is not sufficient information for the watcher 211 to determine if calls can actually be placed with the first computing device 200. Just because the first user 202 is busy does not mean that calls are not to be received from the second computing device 210. Various embodiments of the invention account for such intricate distinctions in presence by indicating both the activity level (e.g., busy or active) and availability level (e.g., connected) of a computing device and/or its corresponding user.

Setting the Access Control List (ACI)

[0042] As described earlier with respect to FIG. 3, when a computing device is not present or a network, but later resumes its activities upon the network, it can access a data structure from the network device to determine which users have subscribed to watch it. At this point, the computing device or its corresponding user decides whether to allow the one or more subscribers access to its presence information. The decision is made known to the server that is handling presence administration for the network device by way of an access control list (ACL). In accordance with another embodiment of the invention, a computing device sets its access preferences with a server via a Set ACL procedure call, as illustrated in FIG. 5.

[0043] The Set ACL procedure call is an executable function or method that specifies the ACL settings for the computing device 300 of the network shown in FIG. 3. As shown, the computing device 300 submits a SERVICE message 304 to a server 102 in order to initiate the setting, or updating, of the ACL 156. The SERVICE message comprises one or more setACL procedure calls 305, which trigger the presence agent 152 operating on the network device 102 to set (update) the ACL 156. Similar to the Set Presence call described above, the setACL procedure call is contained within a SOAP envelope that comprises the body of the SERVICE message. Multiple setACL calls may be contained within a single service message 304 in order to authorize one or more subscribers. When the network device 102 receives the SERVICE message, the presence agent 152 processes it, and the access preferences 306 indicated by the service message 304 are stored within the ACL 156.

[0044] The concept of access control as it applies to this embodiment of the invention will now be discussed in more detail. For each user or group of users of a network, there is a corresponding access control list that specifies what that user or group of users is permitted to do with regard to other users or groups of users. In this embodiment of the invention, there are at least two types of rights: “Incoming” and “Presence.” Incoming rights govern things such as who is permitted to initiate communication with the user. Presence rights govern the ability for a user to monitor whether another user is online. The values to which each of these rights can be set in an embodiment of the invention are as follows: Abbrevi- Right Value ation Meaning INCOMING Allow “A” User having this level of access can invite another user to communicate. Timeout “T” User having this level of access can invite another user to communicate, but the user's real-time communica- tion client program will always time- out the call. This is a polite way of blocking the and equates to the phone “ringing off the hook”. Deny “D” User having this level of access cannot invite another user to communicate. PRESENCE Allow “A” A user can query or subscribe to another user's presence and will be notified when status changes occur Prompt “P” A user having this level of access can attempt to subscribe to another user's presence, but the other user will be prompted for permission Block “B” A user having this level of access may subscribe to another user's presence, but the other user will always appear to be offline. Deny “D” A user with this level of access can- not even subscribe to the other user

[0045] Continuing the discussion of access control, a user or a group of users will also be referred to herein as an “identity.” There are many possible ways to designate an identity. In an embodiment of the invention, the following types of identities exist. Identity Type Meaning ALL All users and groups. DOMAIN All users in this domain URI Used to specify a particular user.

[0046] Each access control list has one or more access control entries. Each access control entry confers one or more rights to an identity. For example, possible access control entries for the user joeb@microsoft.com include: Identity Access Right(s) Meaning ALL INCOMING = Anybody can communicate Allow with joeb@microsoft.com PRESENCE = Nobody can access the Prompt joeb's presence without joeb being prompted to grant permission. DOMAIN INCOMING = Anybody at Microsoft can “microsoft.com” Allow communicate with Joeb PRESENCE = Nobody at Microsoft can Prompt access the joeb's presence without joeb being promp- ted to grant permission. URI INCOMING = The user roberbr@micro- “roberbr@microsoft.com” Deny soft.com is specifically PRESENCE = blocked from any access to Deny joeb.

[0047] According to an embodiment of the invention, the administrator of a network can set a “default” access control list that is applied to all users in a particular group. If an access control entry in the user's personal access control list has the same identity as an access control entry in the default access control list, then the personal access control entry takes precedent over the default access control entry. This merging is done at the server when a user's access control list is retrieved. Client software will only ever see the merged access control list. At install, according to an embodiment of the inventions, the default access control list is set to: Identity Access Right(s) Meaning DOMAIN INCOMING = Allow Allow others in the user's domain “<insert PRESENCE = Allow full access to the user domain Name>” ALL INCOMING = Allow Defaults the access for all other PRESENCE = Prompt users to allow incoming communi- cation, but no access to presence without the owner explicitly granting

[0048] The administrator may also set a “mandatory” access control list that is applied to all users in a particular group.

[0049] Up to this point, the invention has been described with respect to the interaction between one or more users that act as watchers, a computing device, and a corresponding user being watched. However, in many instances the user being watched may have more than one device (registered) with the network device at a time. In such cases, presence information is generated by each of the devices, resulting in several presence documents being generated and exchanged with the server that handles presence administration. For conventional servers, a watcher seeking to obtain presence information pertaining to a user of several devices would receive several individual presence documents. Or, in some instances, the watcher would receive a compound document that simply lists the presence of each device, and nothing more. According to another embodiment of the invention, however, an aggregator component executed by the server that handles presence administration aggregates the presence information of several devices pertaining to a single user into a single presence document. In this way, the watcher is able to obtain a more precise indication of the overall presence of the user. Operation of embodiments of the invention in which this technique is employed is described in the following paragraphs, and with respect to FIGS. 6-8.

[0050] Referring now to FIG. 6, a user 320 employs several telephony devices, including a desktop computer 322, laptop computer 324, and cell phone 326. Each device is registered with a server 328, and generates presence information pertaining to itself and/or the corresponding user 320. To communicate the presence information with watchers 410 (or several watchers), each of the registered devices 322-326 submits a SERVICE message to the server 328 that allows it to invoke the Set Presence procedure call, as described earlier. Upon receiving the SERVICE messages (and corresponding presence documents), the server 328 executes an aggregator module 340 that analyzes each presence document to determine their respective presence priority settings. The presence priority setting is a value calculated using information specified in the presence document for a device, such as from the summation of the availability level 208 and activity level 209 of a presence document 207, to determine the level of presence of the respective device. A higher presence priority setting for a particular presence document indicates a higher degree of presence with respect to a particular computing device. It should be noted that a higher degree of presence is not strictly based upon numeric values, but rather to the meaning associated with a particular availability or activity level. By comparing the presence priority settings of several presence documents, the presence agent 152 can determine which document most accurately reflects the presence of the user 320 and the user's corresponding computing devices 322-326. In turn, the presence agent 152 conveys this information to the watcher 320 to ensure the watcher 320 has access to the most accurate presence information.

[0051] With respect now to FIG. 7, the aggregator component 340 operates upon the server 328 to interpret presence documents generated by one or more registered devices, in accordance with an embodiment of the invention. The aggregator component 340 is implemented as an executable module, such as a dynamic link library (DLL) or computer executable application that is capable of processing presence information. Presence information is generated by the registered devices (desktop 322, laptop 324 and cell phone 326), and conveyed as presence documents 350-354. As described previously with respect to the invention, each presence document comprises information such as an availability level, an activity level, description attribute and any other relevant presence information. Consider the presence document 350 generated by the desktop computer 322, for example, which specifies an availability level 356 equal to 300 and an activity level 358 equal to 000. The activity 358 and availability levels 356 provide an indication of the current state or operation of the desktop computer 322 or user 320, and correspond to the description attributes “online” 360 and “no explicit activity” 362 respectively. Also included within the presence document 350 is any other information 364 pertaining to the presence of the desktop computer 322, such as diagnostic data, user profile data, or the like. Like the desktop computer 322, the laptop computer 324 and cell phone 326 also generate presence documents in a similar fashion.

[0052] Once the server 328 receives the presence documents 350-354, the aggregator component 340 performs a computation to determine which document indicates the highest presence priority setting (event 380). More specifically, the aggregator component 340 calculates the presence priority setting for each document such as by comparing the indicated activity level and availability level values and setting the presence priority setting to that of the highest value. For example, the presence priority settings for the desktop computer 322, laptop computer 324 and cell phone 326 as calculated as shown in TABLE 4 below. TABLE 4 Presence priority settings for the registered devices of FIGS. 6 and 7 Device Availability Activity Description Desktop Computer 322 300 000 online, no explicit activity Laptop computer 324 200 400 connected, active Cell Phone 326 000 000 offline, no explicit activity Aggregate presence 300 400 online, active

[0053] As TABLE 4 shows, the laptop computer 404 has a presence activity setting of 400, the highest of all the computing devices. This setting indicates to the presence agent 152 that the laptop computer 324 is connected to the network for receiving calls, and that the user 320 is actively using the laptop computer 326. Hence, while the desktop computer 322 and cell phone 326 are registered with the server 328, their presence priority settings indicate a lesser likelihood of them engaging in a communication session (e.g., the user 320 is not currently using these devices). In contrast, a higher presence priority setting more explicitly and accurately indicates the presence of the computing devices 322-326 and user 320.

[0054] The aggregator component 340 generates a single presence document that conveys overall presence information related to the single person who owns each of the computing devices 322-326 (event 382). In accordance with yet another embodiment of the invention, this single presence document only specifies the highest availability and activity levels of the computing devices, as illustrated in FIG. 8. Thus, since the highest availability level of the three devices is 300, and the highest activity level of the three devices is 400, the aggregate availability and activity levels are 300 and 400. Hence, the single presence document is generated such that the presence agent can detect which of the user's computing devices 322-326 indicates the highest degree of presence upon the network. In this regard, the single (or aggregate) presence document 400 indicates the availability level 402, activity level 404 and corresponding description attributes 406 and 408 associated with the desktop computer 322 and the laptop computer 400, respectively. Additionally, the other presence information 156 related to each computing device is included within the single presence document 400 just as it was indicated in the original presence documents 350-354. This single presence document 400 is then passed to the presence agent 152 operating upon the server 328 (event 386), where it is stored in an accessible memory location 158 for subsequent retrieval.

[0055] Those skilled in the art will appreciate that the resulting single presence document generated by the aggregator component 340, and having an aggregate availability level of 300 and an aggregate activity level of 400, provides a more accurate indication of presence for users that employ several computing devices. Unlike conventional means for conveying the presence information of several computing devices, the single presence document indicates the presence information associated with each device (e.g., the other relevant information 526), but only reflects the highest availability and activity level of the devices. Consequently, the information that most accurately reflects the presence of the user is what ultimately gets conveyed to any watchers. It will also be appreciated by those skilled in the art that because the aggregator component 340 operates in connection with the presence agent 152, the presence agent can call upon the aggregator component to generate a new presence document in response to common tasks performed by the server 328. For example, the presence agent 152 can activate the aggregator component 340 whenever a REGISTER request is received by the server 328 from a computing device being operated by the user 320, or conversely when a REGISTER request expires. Also, the presence agent 152 in can activate the aggregator component 340 whenever the server 328 receives a new SERVICE message that requires processing. In this way, the most up-to-date presence information for one or more computing devices is continually maintained by the presence agent 152.

[0056] In view of the many possible embodiments to which the principles of this invention may be applied, it should be recognized that the embodiment described herein with respect to the drawing figures is meant to be illustrative only and should not be taken as limiting the scope of invention. For example, those of skill in the art will recognize that the elements of the illustrated embodiment shown in software may be implemented in hardware and vice versa or that the illustrated embodiment can be modified in arrangement and detail without departing from the spirit of the invention. Therefore, the invention as described herein contemplates all such embodiments as may come within the scope of the following claims and equivalents thereof. 

We claim:
 1. A method for enabling the activity and availability of a first computing device on a network to be monitored by a second computing device on the network, the activity representing how active the first computing device is on the network, the availability representing whether or not the first device is available to engage in network telephony with the second device, the method comprising: receiving from the first computing device one or more access preferences indicating which computing devices are permitted to monitor the first computing device; receiving from the second computing device a request to monitor the first computing device, the request being acknowledged regardless of the first computing device's availability or activity; and based on the one or more access preferences, and based on the monitored activity and availability of the first computing device, informing the second computing device of the availability and activity of the first computing device.
 2. The method of claim 1 further comprising: storing information obtained from the request message submitted by the second computing device; and submitting the stored information to the first computing device in response to a request message from the first computing device to obtain the stored information.
 3. The method of claim 2 wherein the first computing device determines whether to grant the second computing device access to the presence information.
 4. The method of claim 1 further comprising receiving and processing one or more procedure calls for initiating the transfer of presence information to a server.
 5. The method of claim 4 wherein the one or more procedure calls correspond to one or more presence documents indicating the activity and availability of the first computing device.
 6. The method of claim 4 wherein the step of processing includes determining at least one of the one or more presence documents that indicates a high presence priority setting, the presence priority setting being indicative of the at least one presence document that best reflects the presence of the first computing device.
 7. The method of claim 1 wherein the step of receiving includes processing the one or more procedure calls for initiating the transfer of the one or more access preferences.
 8. The method of claim 1 further comprising the step of aggregating one or more presence documents received from the first computing device into a single presence document, the single presence document indicating the activity and availability associated with at least one presence document that indicates a high presence priority setting, the single presence document also including presence data associated with the one or more presence documents.
 9. A computer-readable medium having computer-executable instructions for performing the steps recited in claim
 1. 10. A system for conveying presence information about a first user to a second user, the first user having a plurality of computing devices that are capable of generating presence information, the second user having a computing device in communication with a computer network, the system comprising: one or more servers in communication with the computer network and executing programs comprising: a presence agent; an aggregator component; and computer-readable media accessible by the one or more servers and having stored thereon information regarding the second user's desire to monitor the presence of the first user, wherein the presence agent detects which of the plurality of computing devices indicates the highest degree of presence upon the network, wherein the aggregator component generates an aggregate document representing the degree to which the plurality of computing devices is present upon the network, and wherein the one or more servers transmit the aggregate presence document to the second user's computing device based on information stored in the computer readable media.
 11. The system of claim 10 wherein the one or more servers execute a registration service for maintaining registration entries associated with the plurality of computing devices.
 12. The system of claim 10 wherein the computer readable media has stored thereon an access control list that is accessible by the presence agent to maintain access preferences of the first user regarding the plurality of computing devices.
 13. The system of claim 12 wherein the access control list maintains access preferences set by a network administrator, the access preferences of the network administrator having a higher priority than the access preferences of the first user.
 14. The system of claim 10 wherein the presence agent processes one or more subscription messages received from the second user's computing device, the messages indicating the second user's desire to monitor the presence of the first user over the computer network.
 15. The system of claim 10 wherein the presence agent processes one or more service messages, the service messages specifying one or more procedure calls for updating the presence information maintained by the presence agent regarding the plurality of computing devices.
 16. The system of claim 10 wherein the presence agent processes one or more service messages comprising one or more procedure calls for updating the access control list.
 17. The system of claim 10 wherein the presence agent transmits an acceptance message and a notify message to the second device in response to the one or more subscription requests submitted by the second device.
 18. The system of claim 10 wherein the computer-readable media is accessed by the presence agent in response to a request submitted to the presence agent for the information regarding the second user's desire to monitor the presence of the first user, the request being submitted by at least one of the plurality of computing devices.
 19. The system of claim 10 wherein the aggregator component submits the aggregate document to the presence agent in response to one or more service messages received by the presence agent from the plurality of computing devices. 20 A method for generating an aggregate presence document representing the overall presence of a user, the method comprising: receiving a plurality of presence documents generated by a plurality of computing devices of the user, the presence documents including data representative of an activity level and availability level associated with each of the plurality of computing devices; analyzing the plurality of presence documents to identify at least one presence document that has a high presence priority setting; and generating the aggregate presence document based on the activity level and availability level associated with presence document having the high presence priority setting.
 21. The method of claim 20 wherein the step of receiving includes processing one or more service messages associated with the plurality of presence documents.
 22. The method of claim 21 wherein the service messages specify one or more procedure calls for updating the presence information regarding the plurality of computing devices.
 23. The method of claim 20 wherein the step of receiving includes processing one or more messages for initiating or terminating the registration of one or more of the plurality of computing devices.
 24. The method of claim 20 wherein the step of analyzing includes summing an availability level and an activity level specified by the at least one presence document, the resulting sum indicating the degree to which the user is present upon the network.
 25. The method of claim 20 wherein the step of generating includes creating a plain-language description associated with the availability level and including the plain-language description in the aggregate document.
 26. The method of claim 20 wherein the step of generating includes creating a plain-language description in associated with the availability level and including the plain-language description in the aggregate document.
 27. The method of claim 20 wherein the user is a first user, the method comprising: transmitting the aggregate presence document to a computing device of a second user in response to changes in the presence information.
 28. A computer-readable medium having computer-executable instructions for performing the steps recited in claim
 20. 29. A method for generating an aggregate presence document based on presence information generated by one or more computing devices, the aggregate presence document specifying the overall presence of the one or more computing devices, the method comprising: receiving a service message generated by at least one of the computing devices, the service message including one or more presence documents and one or more procedure calls for initiating the transfer of presence information to the presence agent, the presence information including data representative of an activity level and availability level associated with each of the one or more computing devices; analyzing the plurality of presence documents to identify at least one of the presence documents that has a highest presence priority; and generating the aggregate presence document by including data representative of an activity level and availability level associated with the at least one presence document that has the highest presence priority, the aggregate document also including other presence data obtained from the plurality of presence documents.
 30. The method of claim 29 wherein the step of analyzing includes summing an availability level and an activity level specified by the at least one presence document, the resulting sum indicating the presence priority of the at least one presence document.
 31. The method of claim 29 wherein the step of generating includes specifying a description attribute in association with the availability level, the description attribute providing a functional description of the availability level.
 32. The method of claim 29 wherein the step of generating includes specifying a description attribute in association with the activity level, the description attribute providing a functional description of the activity level.
 33. The method of claim 29 further including the step of submitting the aggregate presence document to one or more computing devices having access to the presence information associated with the plurality of computing devices in response to changes in the presence information.
 34. A computer-readable medium having computer-executable instructions for performing the steps recited in claim
 29. 35. A system for communicating presence information related to a first computing device to a second computing device over a network by a presence agent, the presence agent communicating the presence information in response to a request message submitted by the second computing device, the request message requesting access by the second computing device to the presence information, the system comprising: means for receiving from the first computing device a message having one or more procedure calls for initiating the transfer of presence information to the presence agent; means for receiving from the first computing device a message having one or more procedure calls for initiating the transfer of access preferences associated with the first computing device to the presence agent; means for submitting an acceptance message to the second computing device indicating that the second computing device can access the presence information, the acceptance message being submitted regardless of whether the first computing device is present upon the network, and the acceptance message being submitted regardless of the access preferences specified by the first computing device; and means for submitting a notification message to the second computing device, the notification message including a presence document having data representative of an activity level and availability level associated with the first computing device, the notification message being submitted regardless of whether the first computing device is present upon the network.
 36. The system of claim 35 further comprising: means for storing information obtained from the request message submitted by the second computing device regarding the second user's desire to monitor the presence of the first user,; and means for submitting the stored information to the first computing device in response to a request message from the first computing device to obtain the stored information.
 37. The system of claim 35 further comprising means for aggregating one or more presence documents received from the first computing device into a single presence document, the single presence document having data representative of an activity level and availability level associated with at least one presence document that indicates a high presence priority, the single presence document also including presence data associated with the one or more presence documents.
 38. A method for relaying presence information to a subscriber in the absence of a presentity, the presentity operating a presence user agent that generates information indicative of the ability of the presentity to receive calls and indicative of the operating state or tasks in which the presentity is engaged, the method comprising: storing information obtained from a subscriber request message into an accessible memory location, the stored information including one or more values that uniquely identify the subscriber from amongst a plurality of other devices capable of communicating over the network; and submitting the subscriber information to the presentity when the presentity is no longer absent, wherein the presentity makes a determination whether to grant the subscriber access to the information generated by the presence user agent.
 39. The method of claim 38 further comprising submitting the information generated by the presence user agent to the subscriber when a determination is made to grant the subscriber access to the information.
 40. The method of claim 39 wherein the step of determining is made according to access preferences assigned by the presentity.
 41. The method of claim 38 wherein the step of submitting includes transmitting a presence document to the subscriber having data indicative of the ability of the presentity to receive calls and indicative of the operating state or tasks in which the presentity is engaged.
 42. A computer-readable medium having computer-executable instructions for performing the steps recited in claim
 38. 